Even if they had left out that condition, I'm sure there would be ways around it for gaming laptops and they wouldn't necessarily even have to be stupid ways: I could imagine a stupid way of complying being a charging cable with USB-C for the first 100W and proprietary port for the other 200W+.

Just because a law might say that it's got to be technically able to charge from USB-C probably doesn't imply that has to be the only charging port and method, nor even the normal/recommended one. Even on a 200W+ gaming laptop it would be nice sometimes to be able to charge it from USB-C, without pulling out the full charger. If mine supported USB-C charging I could see using it like that when I travel, I might only be using it for half an hour or an hour a day, the 100W would significantly extend the battery runtime, the rest of the time it could be sleeping or off and charging happily back to full from USB-C, so I wouldn't even need to bring the (literal) charging brick.